Our staff at Weston Nurseries is getting a lot of inquiries on rhododendron issues this spring. Our first reaction for this time of the year would normally be “winter burn”. However, it seems the dieback we are seeing is on random branches. After a bit of research, we feel that some of the damage we are seeing now could be Phytophthora dieback. Phytophthora root rot often results in a brown staining of the vascular tissue.
Phytophthora is found typically in sites with poor drainage including heavy clay-type soils. We recommend you apply Jonathan Green’s “Love Your Soil” around the base of the plants with a minimum of three applications. Just apply a couple of hand full each time, 6 to 8 weeks apart. That should, over time, open up the soil to improve drainage.
Also we recommend drenching the soil, (1 teaspoon/gallon of water) with Bonide “Revitalize”. Revitalize is a broad-spectrum preventive biofungicide and bactericide. It utilizes the power of a naturally occurring beneficial bacterium, Bacillus amyloliquefaciens strain D747, to control and suppress fungal and bacterial diseases in plants. This bacterium triggers the plant’s immune response to fight off pathogens, and is a natural product.
Be sure to prune off dead branches, and clean up any debris around the plant.
Keep in mind that it still maybe possible that winter burn and scorch could be the culprit. In that case, more foliage will be “burned” than just the stems.
For more information, please visit https://ag.umass.edu/landscape/fact-sheets/phytophthora-dieback. Or, come by your nearest Weston Nurseries Garden Center for more advice and to pick up a supply of “Love Your Soil” and “Revitalize” today!
